1. Field of the Invention
This invention relates to the dry transfer of printed graphics onto receptive substrates.
2. The Prior Art
Various dry transfer techniques have been developed for applying graphics to substrates. Of these, perhaps the most common involves the printing of graphics on carrier films which are then adhesively secured to the substrates, typically by pressure sensitive adhesives. The printed films may be applied in sheet or roll form to cover large areas, or they may be die cut into labels or decals for application to smaller areas.
A different approach is described in U.S. Pat. No. 4,517,044 (Arnold) where a dry transfer decal is produced without a carrier film by successively printing the underside of a base sheet with a cross-linked abrasion resistant carrier coat, the graphics, and a high tack pressure sensitive adhesive. Once the adhesive is applied to the substrate, the base sheet is removed from the carrier coat, leaving as a transferred residue the graphics protected by the carrier coat and adhered to the substrate by the adhesive.
There are several drawbacks to the Arnold approach. First, the immediate bond created by the high tack pressure sensitive adhesive prevents the decal from being removed from and repositioned on the substrate during initial application. This can be particularly troublesome when applying large area graphics in sheet or roll form.
The thickness of the carrier coat, which ranges from 0.005 to 0.020 inches, contributes disadvantageously to the overall thickness of the decal, thus precluding its use as an underlayer beneath transparent top coats.
Also, where the graphics are intended only for temporary display, to be replaced after a relatively short period of time by other fresh graphics, the abrasion resistance of the cross-linked carrier coat resists removal, making it necessary to resort to more rigorous, costly and time consuming removal techniques and procedures.